Carburetors are used to provide fuel and air mixtures for a wide range of two-cycle and four-cycle engines, including hand held engines, such as engines for chain saws and weed trimmers, as well as a wide range of marine engine applications, for example. Diaphragm-type carburetors are particularly useful for hand held engine applications wherein the engine may be operated in substantially any orientation, including upside down. Float bowl carburetors are typically used in applications wherein they are not inverted like in lawn mowers, tractors and the like. In an attempt to achieve more efficient operation and to reduce exhaust emissions from engines, valves have been used to regulate the fuel and air mixture during at least some operating conditions.